function Tab(el) {
  this.el = document.querySelector(el);
  this.init();
}
Tab.prototype.init = function() {
  this.titleOver();
};
Tab.prototype.titleOver = function() {
  let ulLiObjs = this.el.querySelectorAll("ul li");
  ulLiObjs.forEach((item, i) => {
    item.onmouseover = () => {
      this.tbTitle(ulLiObjs, i);
      this.tbContent(i);
    };
  });
};
Tab.prototype.tbTitle = function(ulLiObjs, i) {
  this.el.querySelector("ul li.active").className = "";
  ulLiObjs[i].className = "active";
};
Tab.prototype.tbContent = function(i) {
  this.el.querySelector("ol li.active").className = "";
  let olLiObjs = this.el.querySelectorAll("ol li");
  olLiObjs[i].className = "active";
};
